1. Field of the Invention
The present invention relates to a speech synthesizing system and method which provide a more natural synthesized speech using a relatively small waveform database.
2. Description of the Prior Art
In a conventional speech synthesizing system in a certain language, each of speeches is divided into voice segments (phoneme-chained components or synthesis units) which are shorter in length than words used in the language. A database of waveforms for a set of such voice segments necessary for speech synthesis in the language is formed and stored. In a synthesis process, a given text is divided into voice segments and waveforms which are associated with the divided voice segments by the waveform database are synthesized into a speech corresponding to the given text. One of such speech synthesis systems is disclosed in Japanese Patent Unexamined Publication No. Hei8-234793 (1996).
However, in a conventional system, a voice segment is to be stored as a different one in the database even if there exist in the database one or more voice segments the waveforms of which in the most part are the same as that of the voice segment if the voice segment differs from any of the voice segments which have been stored in the database, which makes the database redundant. If the voice segments in the database are limited in number in order to avoid the redundancy, any of the limited voice segments has to be deformed for each of lacking voice segments in a speech synthesis process, causing the quality of the synthesized speech to be degraded.
It is an object of the invention to provide a speech synthesizing system and method which permits a waveform database to be made smaller in size while providing a satisfactory speech synthesis quality by avoiding any speech segment deformation for a lacking speech segment in the waveform data base.